There is a type of inkjet head in which adjacent ink chambers share an actuator. This inkjet head is called a share mode type. In this type of inkjet head, a plurality of ink chambers which are arranged in parallel are divided into (n+1) sets at intervals of n (where n is 2 or more). A driving device changes a phase for driving each set and selectively drives each ink chamber in the same set. When the ink chamber is driven, ink droplets are ejected from a nozzle which communicates with the ink chamber.
An ink chamber B which is adjacent to a driven ink chamber A is not driven. However, in the ink chamber B, a partition on one side which separates the ink chamber A therefrom is deformed. At this time, if a partition on the opposite side is also deformed, there is a probability that ink droplets may be erroneously ejected from a nozzle which communicates with the ink chamber B. For this reason, the driving device simultaneously drives an ink chamber C which shares the partition on the opposite side as an actuator, at the same potential as a potential of the ink chamber B so that the partition on the opposite side of the ink chamber B is not deformed. In addition, if the ink chamber A is driven but does not eject ink, the ink chamber A is required to be simultaneously driven at the same potential as potentials of the ink chambers B adjacent to both sides thereof so that the partitions of both ends of the ink chamber A are not deformed. For this reason, if no ink chambers A eject ink, a phenomenon may occur in which all the ink chambers are simultaneously driven at the same potential.
In the share mode type inkjet head, a plurality of ink chambers which are separated from each other by partitions made of a piezoelectric material are arranged in parallel. An electrode is disposed on wall surfaces of each ink chamber. Therefore, the inkjet head is equivalent to a series circuit of capacitors from the electrical viewpoint. Floating capacitors occur between the capacitors which are connected in series in this circuit. The floating capacitors are charged or discharged when voltages with the same potential are simultaneously applied to both ends thereof in a state in which the capacitor is interposed therebetween. Noise current is generated in the head due to the charge or discharge of the floating capacitors, and thus power is wastefully consumed.